Composite alloy



NGV' 17 1953 T. E. LEON-ris ET Ar.

COMPOSITE ALLOY Filed Aug. 16, 1950 IN V EN TORS. Thomas E. Leon/'s BYRoer `S`. Busk TTORNE YS IIIHQ Patented Nov. 17, 1953 GOMPO SITE ALLOYThomas E. Leontis and Robert S. Busk, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., acorporation of Dela- Application August 16, 1950, Serial No. 179,775

(Cl. .Z9-182.2)

8 Claims.

The invention relates to a magnesium-base alloy article. It moreparticularly concerns a composite metal body comprising a magnesiumbasemagnesium-zirconium alloy but having enhanced tensile strength and otherdesirable characteristics including the light weight exhibited byconventional magnesium-base alloys.

The term magnesium-base alloy used herein means a magnesium alloycontaining at least 80% of magnesium by weight.

The invention is predicated upon the ydiscovery that by die-expressingat elevated temperature Vthe magnesium-base magnesium-zirconium alloy inparticulated form in admixture with particulated silver, a high strengthcomposite alloy ex- -trusion is obtained. The composite alloy extrusionhas the same compactness and integrity as the usual magnesium-base alloyextrusions made by extruding a solid mass, such as an ingot of amagnesium-base alloy, but the metallographic structure of the compositeproduct is uniquely different. Metallographic examination reveals a newtype of structure in a magnesium-base alloy article. The structure isessentially multimetallic. Each of the two particulate metals of thelmixture which is extruded is changed into the form of elongatedparticles with the long axis parallel to that of the extrusion and theseelongated particles are all welded one to the other into a solid masswithout voids. The invention vthen consists of the compositemagnesium-base alloy product and method of making the same herein fullydescribed and particularly pointed out in the claims, the followingdescription setting forth several modes of practicing the invention.

In carrying out the invention, the magnesiumzirconium alloy used maycontain from about 0.1 to 0.8 per cent of zirconium. A preferable amountis about 0.3 per cent. 'I'he zirconiumcontaining magnesium-base alloymay also contain up to 2 per cent of cerium or mischmetal or up to 8 percent of zinc, or up to l per cent of calcium or combinations of thesealloying Vmetals, the total amount of alloying metal not exceeding about12 per cent. The alloy is used in particulate form such as may beobtained by grinding or preferably by atomization. The

atomized form may be made by impinging a jet of a cool gas, e. g.natural gas, against a thin, falling stream of the molten alloy.Particles coarser than those passing through about a l to mesh standardsieve are screened out and preferably also particles iiner than about200- mesh In the atomized form the particles consist of ne rapidlysolidified round particles having an extremely line grain structure.

The silver may be comminuted in any convenient manner, e. g. grinding,so as to form it into particles as fine as and preferably finer thanthose of the magnesium-zirconium alloy.

The two particulated metals above-described are intimately mixed as bytumbling the two particulated metals in a tumbling barrel or in anyother convenient manner, prior to the extrusion operation. Theproportion of particulate silver may range from about 0.1 to 6 per centby weight of the mixture. A preferred range of proportions is about 2 to4 per cent, 3 per cent being generally the most desirable proportion.

The mixture of the vparticulated metals is charged into the heatedcontainer of a conventional ram extruder having a suitable containersize and die opening to produce a substantial reduction in area. Thereduction in area produced, as expressed by the ratio of the`crosssectional area of the container to that of the die opening, has amaterial effect on the mechanical properties of the composite extrusionobtained. In general, the higher the ratio the better the mechanicalproperties. A desirable ratio is at least 30 to 1, although ratios ashigh as to 1 or more may be used.

The invention may be further illustrated and explained in connectionwith the accompanying drawing in which:

Fig. l shows a schematic sectional elevation of an extrusion apparatussuitable for use in practicing the invention;

Fig. 2 is a similar view to Fig. l showing a modification of theapparatus; and

Fig. 3 is a similar View to Fig. 1 showing another modification of theapparatus.

As shown, the apparatus comprises, in its three forms, an extrusioncontainer l adapted to coniine a charge 2 of the mixture of theparticles of the two metals to be co-extruded. The container is providedwith a heating element 3. In Fig. 1, one end of the container I isclosed by the die plate 4 in which is provided the die opening 5. Inthis form of the apparatus, the charge 2 is caused to be compacted inthe container and extruded through the die opening 5 by application ofpressure by means of the dummy block 6 forced into the bore 1 ofthecontainer by the ram 8 to form the composite alloy extrusion 9.

In the form of the apparatus shown in Fig. 2,

the container l is closed atone end by the plate l0. The other end ofthe A.container receives the die block Il carried by the hollow ram l2which forces the die block into the container causing the charge 2 to becompacted and to extrude through die opening I3 to form the compositealloy extrusion I4 which extends into bore I5 composite alloy extrusion.It should be noted that the composite alloy has the unique advantage ofretaining high strength after prolonged heating at high temperature.This property en-l of the hollow ram I2. 5 ables the composite alloy tobe hot worked as In the modification of Fig. 3, the container I inbending, forging, rolling, drawing with reis closed at oney end by aplate I6. The charge duced loss of strength. 2 is extruded as a tubularcomposite alloy ex- We claim: trusion II through the annulus I0 aroundthe 1. The method of making a solid composite die block I9 while theblock is forced into the 10 article comprising magnesium alloyed withzircontainer by the ram 20. conium which comprises forming a mixture ofThe forms of the apparatus shown are convena zirconium-containingmagnesium-base alloy in tional. particulate form and silver inparticulate form,

By putting a charge of the. mixture of particles. said alloy containing0.1 to 0.8 per cent of zirof the two metals involved under pressurewhile conium,: the balance being at least 88 per cent of at heat, aswith the apparatus shown, the mixmagnesium, andv die-expressing themixture at a ture of metal particles is compacted but not subtemperaturebetween 600 and 710 F., the amount jected to further mixing beforeextrusion. The of silver i'n the mixture being from 0.1 to 6.0 permetals in the charge as individual metal parcentof the weight of themixture. ticles become welded together without voids and 2. The methOdaccording t0 Claim 1 in Which without losing their original distinctivecompothe zirconium-containing magnesium-base alloy sition except at thesurface of the unionof the also contains up to 2. per cent of cerium.diflerent kinds ofparticles which become ex- 3. The method according toclaim 1 inV which tended and lengthened during. extrusion. At thezirconium-containing magnesium-base alloy these surfaces duringextrusion some interd also contains up to 8 per cent of Zinc.. mixingoccurs, as by diffusion, between the par- 1. The method according toclaim 1 in which ticles. of the dierent kinds of metal in the exthezirconium-containing magnesium-base allOy tl'usion charge, formingcomposite alloy. In this Aalso contains up 150.1 per cent of calcium..diffusion some of the silver diffuses into the sur- 5- A Compositemetal body COIlSStiIlg 0f two faces of the magnesium-zirconiiun alloypar- S0 paltlculated metals one of the metals being a vticles and someof the magnesium-zirconium almagnesium-base alloy containing from. 0.1Vto 0.8 loy particles diffuses into the silver. The cornper cent ofzirconium and the balance being at posite alloy can be worked asv byrolling, forging, lea-St 88 per cent of magnesium, the other beingpressing, etc.. like conventional magnesium-base elementary silver inamount between 0.1 and 6 alloys.. per cent by weight of the metal body,the par- The following examples are illustrative of the ticles of eachof the metals being elongated, invention. orientated in the samedirection, and welded to- Table Mechanical Properties1 oi Extruslons in1,000s p s. i. Composition of Extrusion Charge of Commmuted A Mixed withCom- Extrusion Exgggmuted SHV .4s Extruded Aged H. T H. T. A

(fetg' Annysisofli 'rYs Ts 'rYs 'rs TYs 'rs TYs Ts camper. lst/min 99.9o.33%2r,13a1.Mg 0.1 27 37 2s 39 23 33 23 39 67o 2 99.5 .do 0.5 27 36 2736 31 3s 3o 3s 68o 2 6.o 24 l3 31 33 37 4s 3 43 63o 2 none 26 36 29 372s 37 23 36 63o 2 0.1 26 36 27 33 25 35 27 36 71o 4 0.5 27 37 2s `36 2531 27' 36 71o 2 6.0 24 35 23 37 24 32 27 36 710A 3 none 27 36 27 36 2o29 22 3o 075 3 n.5 46 47 46 5o 39 42 4o 43 665` 2 1.o 3s 41 42 45 40 4340 43 665 2 3.o 43 47 49 5o 46 47 45 43 663 2 7 6.o .45 47 45 47 39 4343 44 665 0,5 Blank G, none 44 47 45 46 29 37 27 3s 665 2 g 3.o 26 37 2733 27 39 son 0 5 Blank 7 none 23 35 25 36 26 36 600 0. 5

l Aged=Heated 16 hours at 350 F. H. T.'=Heated 1 hour at 750 F.

H. T. A.=Heated 1 hour at 750 F. followed by heating for 16 hours at 350F.

In Examples 1 to 7 and blanks 1 to 6, the container of the extrusionapparatus had a diameterV of 1/2 inch and the die opening was 0.086inch, thereby producing composite alloy wire 0.086 inch in diameter(reduction in area 34:1) In Example 8 and blank 7, the same sizecontainer was used but the die opening was 0.07 inch, thereby producing`composite alloy wire 0.07 inch .diameter (reduction in area :1).-Referring to the table, it Will be seen that the benecial eects ofadding the silver to the `magnesium-zirconium alloy, in the mannerdescribed,

areespecially noticeable on heat treating the 6 cle to a further heattreatment in which the FOREIGN PATENTS igesosbjected to a prolongedheating at Number Country Date THOMAS E' LEONTIS. 5 0,1 6 Great BritainJune 26, 19

570,906 Great Brltam July 27, 1945 ROBERT S- BUSK- 5 625,364 GreatBritain June 2'1, 1949 References Cited in the file 01 this patent OTHERREFERENCES UNITED STATES PATENTS Treatise on Powder Metallurgy byGoetzel, V01. 2, pp. 500, 740, 741. Published in 1950. NluggellstouNtame Jurae 1933 10 Symposium on Powder Metallurgy, Buffalo 2024767Jerie't-a'fm11i-Dec.17 1935 Spring Meeting March 3 1943 Published by2205865 Schwarzko June 25 1940 American Society for Testing Materials,Phila- 2332277 l Stern Oct-, 29, 1943 delphlaf P31-, pages 42 and 43-2,355,954 Cremer Aug. 15, 1944 15

5. A COMPOSITE METAL BODY CONSISTING OF TWO PARTICULATEED METALS ONE OFTHE METALS BEING A MAGNESIUM-BASE ALLOY CONTAINING FROM 0.1 TO 0.8 PERCENT OF ZIRCONIUM AND THE BALANCE BEING AT LEAST 88 PER CENT OFMAGNESIUM, THE OTHER BEING ELEMENTARY SILVER IN AMOUNT BETWEEN 0.1 AND 6PER CENT BY WEIGHT OF THE METAL BODY, THE PARTICLES OF EACH OF THEMETALS BEING ELONGATED, ORIENTATED IN THE SAME DIRECTION, AND WELDED T